The present invention relates to electronic systems and more particularly to system configurations which provide RF isolation and shielding among various segments of such systems.
There are many electronic systems and subsystems in which it is important to prevent the coupling of RF signals between different, sensitive segments of the system or subsystem in order to prevent undesired oscillations, misapplication of signals and interference between different signals. Hereinafter, the term system is used to include both systems and subsystems. Such systems include high gain amplifiers such as intermediate frequency IF amplifiers in communication systems; other systems which are sensitive to noise such as low signal amplitude, high gain preamplifiers; systems in which control signal leakage or contamination can cause undesired system operation; and other systems where contamination of one signal by another must be prevented. Many systems which are only moderately sensitive to the coupling of RF signals are fabricated in a single enclosure. However, systems which are particularly sensitive to interfering RF signals are normally designed and manufactured with the sensitive segments in physically separate enclosures which are interconnected by shielded cables in order to provide the required RF isolation among them.
In particular, the primary technique used to obtain RF isolation in highly RF sensitive systems is to place each sensitive circuit segment on its own printed circuit board and to place that circuit board in an individual shielding enclosure to isolate it from other system segments.
It is known in strip transmission line structures in which a conductor is suspended between two ground planes to use a row of conductive rods which extend between the ground planes to RF shield an individual conductor from other conductors.
In recent years a need has developed for the fabrication of compact lightweight systems for use in aircraft, in space and in other locations where space and weight capacity are severely limited. The prior art technique of obtaining RF isolation via physical separation in individual enclosures is largely incompatible with the need for compact, lightweight systems. In the past, it has been necessary to accept increased size and weight in exchange for obtaining high RF isolation among system segments.
It is desirable to provide electronic systems which ensure complete RF isolation of selected system segments from each other while allowing the system to be fabricated in a compact, unitary manner.